Ceramic, cermet and glass materials are superior in high temperature resistance, wear resistance and corrosion resistance, and can be sufficiently used under severe circumstances in which metal and organic materials cannot be used. Ceramic, cermet and glass materials are basically hard and brittle, so that the mechanical processing is difficult and requires a high cost. The technical fields of use for these materials have been thus limited.
It has been studied to use a ceramic, cermet or glass material in a limited part and combine this with another material such as metal to improve the usability and to reduce the overall cost. It has been, however, observed that the materials are hard and brittle such that a stress, which is induced at the bonded position of the brittle material and another material due the difference of thermal expansion coefficients, often results in fracture, The application fields of the brittle materials have been thus very limited.
It has been tried to produce composites of various brittle materials and metals to solve the above problems. For example, according to Japanese patent No. 1809176B, for joining a ceramic material and an A1 member, it is proposed that an iron series alloy member and an intermediate metal member each having a thermal expansion coefficient between those of the ceramic material and alloy member are provided therebetween to provide a composite body of ceramic and metal whose thermal stress is reduced.
Further, according to patent No. 2050428B, it is proposed that ceramic and metal materials are joined with each other through an intermediate layer of a composite material having a specific composition to provide a bonded article of metal and ceramic having improved thermal resistance, reliability and a longer life.